1. Field of the Invention
The present invention relates to a terminal unit, a position display method, an information providing system and an information providing method which are suitably applicable to an navigation system.
2. Description of the Related Art
FIG. 17 shows an example of an arrangement of an navigation system using a prior portable terminal. A plurality of low orbiting satellites 10A and 10B (although two in the illustration, in general at least three low orbiting satellites) constitute a GPS (Global Positioning System) and orbit around the earth at a relatively low position. A portable terminal 11 receives radio waves emitted from the low orbiting satellites 10A, 10B to calculate its own present position.
FIG. 18 is an illustration of an example of an arrangement of the portable terminal 11. In FIG. 18, a CPU 31 executes various processes in accordance with programs stored in a ROM 32, and a RAM 33 stores data, programs and others necessary for the various processes the CPU implements. An input section 40 is used when the user of the portable terminal 11 inputs given instructions, and a display section 38 is composed of a liquid crystal display device or the like to display pictures such as given letters and graphic patterns. A receiving circuit 36 receives, through an antenna 35, radio waves outputted from the low orbiting satellites 10A, 10B to output a demodulated signal to an arithmetic circuit 37. The arithmetic circuit 37 operates the signal fed from the receiving circuit 36 to obtain the present position (latitude and longitude) and outputs it to the CPU 31. A reproducing unit 39 reproduces map data recorded in a recording medium such as a CD-ROM and makes the display section 38 display it. An interface 34 performs the interface processing for the arithmetic circuit 37, the display section 38, the reproducing unit 39 and the input section 40.
In this example, the display section 38 displays the map data the reproducing circuit 39 reproduces from the CD-ROM, and when taking in the position information expressed with the latitude and the longitude from the arithmetic circuit 37, the CPU 31 produces a picture of a present position indicating mark corresponding to that position and outputs the picture via the interface 34 to the display section 38 which in turn, displays the picture. Thus, the map and the present position appear on the display section 38.
FIG. 19 shows another example of an arrangement of a navigation system. A portable terminal 20 transmits and receives radio waves to and from the nearest base stations 21A, 21B and gains access through a network 23 with an exchange 22 to, for example, a given database 24. FIG. 20 is an illustration of an example of an arrangement of the portable terminal 20. In FIG. 20, a CPU 61 executes various processes in accordance with programs stored in a ROM 62 and suitably makes a RAM 63 store data or the like. An input section 67 is operated for when the user of the portable terminal 20 inputs given instructions. A reproducing unit 66 reproduces map data recorded in a CD-ROM or the like so that the map data is displayed on a display section 65. A communication circuit 69 establishes communications with the neighboring base station of the base stations including the base stations 21A, 21B. An interface 64 carries out the interface processing for the reproducing unit 66, the display section 65, the input section 67 and the communication circuit 69.
In this example, as well as the FIG. 18 portable terminal 11, the reproducing unit 66 reproduces a map from the CD-ROM and the display section 65 displays it, whereas a method of detecting the present position differs from that in the FIG. 18 terminal 11. That is, in this example, when establishing communication via the communication circuit 69 to the adjacent base station (for example, the base station 21A), the CPU 61 gets an ID (IDentification) number of the base station 21A. Since the base stations 21A, 21B are all equipment fixed at given locations, the positions thereof are known in advance. Accordingly, the position of the base station which is in connecting relation to the portable terminal 20 can be specified by the ID number thereof. For instance, if the RAM 63 stores a corresponding table between the ID numbers of the respective base stations and the positions of the base stations, when receiving the ID number of a base station, the CPU 61 can find the position corresponding to the ID number referring to the table the RAM 63 retains therein. In addition, the CPU 61 can make the display section 65 display the obtained position as the present position.
There is a problem which arises with any one of the conventional portable terminals, however, in that the system increases in size and cost because the reproducing unit 39 or 60 is designed to reproduce the map data. Further, in the case of the FIG. 20 portable terminal 20, since the RAM 63 needs to store the table representative of the corresponding relationship between the ID numbers of the respective base stations and the positions thereof, the increase in the capacity of the RAM 63 is necessary not only to increase the dimension of the portable terminal 20 but also to raise the cost thereof. Still further, in the case of the FIG. 18 portable terminal 11, since the arithmetic circuit 37 is made to calculate the latitude and longitude of the present position, the circuit scale of the arithmetic circuit 37 increases in size and in cost.